Answer
a) $S(t)= 142\cdot (0.956)^t$
b) $79.11$ acres
c) $17.93$ acres
Work Step by Step
The problem describes an exponential function with the following parameters.
\begin{equation}
\begin{aligned}
a&= 142\\
r&= 4.4\%= 0.044\\
b&=1-r = 0.956
\end{aligned}
\end{equation}
a) Hence, a model of the glacier is
\begin{equation}
\begin{aligned}
S(t)&= a\cdot b^t\\
&= 142\cdot (0.956)^t
\end{aligned}
\end{equation} b) Set $t= 13$ for the year 2020 since 2007.
\begin{equation}
\begin{aligned}
S(13)&= 142\cdot (0.956)^{13}\\
&=79.11
\end{aligned}
\end{equation} The glacier decreased to about $79.11$ acres in 2020.
c) Set $t= 3$ for the year 2010 since 2007.
\begin{equation}
\begin{aligned}
S(13)&= 142\cdot (0.956)^{3}\\
&=124.07
\end{aligned}
\end{equation} The glacier decreased by $142-124.07= 17.93$ acres between 2007 and 2010.
